feat(网格): 支持不完整末行铺满布局

README.md

@@ -114,8 +114,8 @@ const data = ref<WaveformData>({
 | `xDomainStrategy`                 | `WaveformXDomainStrategy`                   | `{ type: 'data' }`                                      | 自动 X 轴视口范围策略                         |
 | `yDomain`                         | `[number, number]`                          | 未设置                                                  | 所有波形的固定 Y 轴范围                       |
 | `yDomains`                        | `Record<string, [number, number]>`          | 未设置                                                  | 按 track/series ID 配置固定范围               |
-| `grid`                            | `WaveformGridOptions`                       | `{ rowCount: 2, columnCount: 1, showPagination: true }` | 网格和分页                                    |
+| `grid`                            | `WaveformGridOptions`                       | `{ rowCount: 2, columnCount: 1, showPagination: true, fillIncompleteLastRow: false }` | 网格和分页                                    |
-| `axes`                            | `WaveformAxesOptions`                       | 轴线均显示                                              | X/Y 轴基线显隐与 X 轴 label 格式化            |
+| `axes`                            | `WaveformAxesOptions`                       | 轴线均显示                                              | X/Y 轴基线、Y 轴分割数与 X 轴 label 格式化    |
 | `rendering`                       | `WaveformRenderingOptions`                  | `{}`                                                    | 降采样与点/误差棒间距                         |
 | `title` / `legend` / `frameStyle` | 对应公开类型                                | 未设置                                                  | 标题、图例和图框样式                          |
 | `frameNumber`                     | `string \| number`                          | 未设置                                                  | 图框水印内容                                  |
@@ -208,7 +208,8 @@ import 'waveform-analysis/style.css'
 
 范围优先级为 `trackId` 配置、`seriesId` 配置、全局 `yDomain`、数据自动范围。上下限必须
 是两个有限且不相等的数字；倒序范围会自动调整为升序，无效配置会回退到下一优先级。
-固定范围会精确作为坐标域使用，不会经过 D3 的 `nice()` 扩展。
+固定范围作为 Y 轴刻度算法的初始范围；轴会按漂亮步长经过 D3 的 `nice()` 扩展，确保主刻度
+等间距。原始数据和传入的范围值不会被修改。
 
 单值轴叠加模式会合并同一根轴上所有可见系列的有效范围；多值轴模式按系列分别使用配置，
 超过四根轴后复用第 4 根轴的系列会取范围并集。隐藏系列不参与公共范围合并。
@@ -216,6 +217,16 @@ import 'waveform-analysis/style.css'
 固定范围存在时，对应图框的 Y 轴不会被平移或视口重置覆盖；X 轴缩放、平移和重置保持原有
 行为。运行时更新或移除 `yDomain` / `yDomains` 会立即重新布局，移除后恢复自动范围。
 
+### Y 轴自动等分
+
+Y 轴默认显示 5 个主刻度（包含上下端点），并使用类似 ECharts 的 `1 / 2 / 5 × 10ⁿ` 漂亮
+步长，保证主刻度之间数值等间距。可以通过 `axes.y.splitNumber` 指定主刻度总数；每条
+Y 轴会独立计算：
+
+```vue
+<WaveformChart :data="chartData" :axes="{ y: { splitNumber: 5 } }" />
+```
+
 ### 缩放后按可视区间加载数据
 
 组件支持 Plotly 风格的矩形框选缩放：在 zoom 模式下按住鼠标左键拖拽，松开后同时缩放
@@ -253,6 +264,20 @@ X 轴且包含多个轨道时使用按稳定 track ID 索引的 `yRanges`。平
 重置组件内部缩放并触发 `zoom-reset`；调用方应在事件中取消区间请求并恢复首次完整数据。
 外部重置按钮也可以通过模板引用调用组件公开的 `resetViewport()` 方法，然后执行相同的数据恢复逻辑。
 
+宿主在替换局部数据后如果需要恢复之前保存的 X 视口，可以调用公开的
+`setViewportDomain(domain, trackIndex?)`。传入范围使用原始秒坐标，组件会按当前数据边界、
+`xDomainStrategy`、`minZoomSpan` 和 `minVisiblePoints` 重新约束；无效范围会被忽略。共享
+X 轴模式直接传入一个范围，独立模式可以按实际 `trackIndex` 分别设置（省略 `trackIndex`
+时应用到当前所有图框）：
+
+```ts
+chartRef.value?.setViewportDomain(previousDomain)
+chartRef.value?.setViewportDomain(trackDomain, trackIndex)
+```
+
+建议在 `data` 引用更新后调用该方法。组件也会在数据引用变更时重投影当前内部视口，避免新
+数据边界使旧 transform 失效；`resetViewport(trackIndex?)` 的既有行为保持不变。
+
 没有显式配置初始范围时，可以通过 `xDomainStrategy` 将数据范围扩展为便于阅读的视口端点。
 默认的 `{ type: 'data' }` 保持数据最小值和最大值不变；`type: 'nice'` 使用固定刻度数量计算
 易读边界，且只扩展视口，不修改原始点位、tooltip、标注或缩放事件值：
@@ -284,6 +309,34 @@ X 轴且包含多个轨道时使用按稳定 track ID 索引的 `yRanges`。平
 Tooltip 每个系列按 `炮号：通道  (x:值 y:值)` 格式显示。`WaveformSeries.shotNo` 为空或未提供时，
 炮号显示为“未配置炮号”；Tooltip 不显示单位和误差附加文本。
 
+### 纵轴单位
+
+可在每个 `WaveformSeries` 上设置可选的 `unit`，单位会显示在对应 Y 轴的顶部刻度中：
+
+```ts
+const chartData = {
+  kind: 'series',
+  series: [
+    {
+      id: 'voltage',
+      name: '电压',
+      unit: 'V',
+      data: {
+        kind: 'points',
+        points: [
+          { x: 0, y: 1200 },
+          { x: 1, y: 3000 },
+        ],
+      },
+    },
+  ],
+} satisfies WaveformData
+```
+
+当 Y 轴使用科学计数法时，顶部刻度格式为 `E+03 (V) 3`；未使用科学计数法时，格式为
+`(V) 3`。单位为空、全为空白或未配置时，不显示 `(单位)`，例如仍显示为 `E+03 3` 或 `3`。
+多 Y 轴模式下，每根轴使用该轴首个 series 的单位。
+
 ### 线型、点型与误差棒
 
 每条序列可以独立设置连线方式、数据点符号和误差棒：
@@ -491,6 +544,10 @@ scale 定位零线：
 `grid` 控制独立图框的行列数（范围 `1–10`）以及是否显示分页器。默认值为 `2` 行、
 `1` 列并开启分页；当图框数量超过网格容量时，分页器会显示在图表右下角。
 
+`fillIncompleteLastRow` 默认关闭。开启后，分页容量仍由 `rowCount * columnCount` 决定；
+最后一页或未满页会移除没有数据的整行，并将最后一行的实际图框等宽铺满可用宽度。例如 2 列
+网格的最后一行只有一个图框时，该图框会占满整行。完整页和关闭该选项时的布局保持不变。
+
 还可以通过 `trackLines` 按轨道 ID 分别控制水平/垂直网格线的显隐和颜色。颜色未配置时，
 继续使用组件默认的主/次网格颜色：
 
@@ -501,6 +558,7 @@ scale 定位零线：
     rowCount: 2,
     columnCount: 2,
     showPagination: true,
+    fillIncompleteLastRow: true,
     trackLines: {
       voltage: {
         horizontal: false,
@@ -655,7 +713,7 @@ async function importAnnotationFile(file: File) {
 字段无效时会抛出 `TypeError`，不会返回部分结果。导入包含未知 `seriesId` 的标注是允许的，
 对应曲线加载后会恢复显示。文件选择、错误提示和下载由业务层实现。
 
-X 轴刻度和左右端点先按 `timeUnit` 转换为秒或毫秒，再显示为不带分组符和科学计数法的完整普通十进制值，并可通过 `axes.x.labelFormatter` 自定义。Y 轴会根据完整显示域选择格式：最大绝对值在 `[0.01, 100)` 时显示两位普通小数；大于等于 `100`，或大于 `0` 且小于 `0.01` 时，刻度显示两位缩放值，并在轴末端单独显示共享倍率 `E±NN`，多 Y 轴分别计算倍率。tooltip 使用最多 4 位小数的本地化普通数字并省略无意义尾零；标注编辑器的 X 坐标跟随 `timeUnit` 并固定 3 位小数，Y 坐标显示完整普通十进制。所有格式化都只发生在展示层，内部坐标值保持原始精度。
+X 轴刻度和左右端点先按 `timeUnit` 转换为秒或毫秒，再显示为不带分组符和科学计数法的完整普通十进制值，并可通过 `axes.x.labelFormatter` 自定义。Y 轴会根据完整显示域选择格式：最大绝对值在 `[0.01, 100)` 时显示两位普通小数；大于等于 `100`，或大于 `0` 且小于 `0.01` 时，刻度显示两位缩放值，并在顶部刻度单独显示共享倍率 `E±NN`。如果 series 配置了 `unit`，顶部刻度会在倍率后追加 `(单位)`；没有科学计数法时也会显示 `(单位)`，多 Y 轴分别使用对应轴首个 series 的单位。tooltip 使用最多 4 位小数的本地化普通数字并省略无意义尾零；标注编辑器的 X 坐标跟随 `timeUnit` 并固定 3 位小数，Y 坐标显示完整普通十进制。所有格式化都只发生在展示层，内部坐标值保持原始精度。
 标注框默认布局在采样点正上方，只做绘图区边界裁剪；文本框通过连接箭头指向标注位置，多个标注重叠时可通过拖动手动避让。
 
 ## 事件

package.json

@@ -1,6 +1,6 @@
 {
   "name": "waveform-analysis",
-  "version": "0.1.38",
+  "version": "0.1.42",
   "main": "./dist/index.cjs",
   "module": "./dist/index.js",
   "types": "./dist/types/index.d.ts",

src/components/WaveformChart.vue

@@ -36,6 +36,7 @@ const controller = useWaveformChartController(props as ResolvedWaveformChartProp
 
 defineExpose({
   resetViewport: controller.resetViewport,
+  setViewportDomain: controller.setViewportDomain,
 })
 </script>
 

src/components/annotation/WaveformAnnotationEditor.css

@@ -1,3 +1,33 @@
+/* The modal is teleported to body. Keep its entire subtree namespaced so host
+   application resets (for example `button { ... }`) cannot change the editor. */
+:global(.waveform-annotation-editor-root),
+:global(.waveform-annotation-editor-root *) {
+  box-sizing: border-box;
+}
+
+:global(.waveform-annotation-editor-root) {
+  color: #344054;
+  font-family:
+    -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial,
+    'Noto Sans', sans-serif;
+  line-height: 1.5715;
+  text-align: left;
+  text-transform: none;
+}
+
+:global(.waveform-annotation-editor-root button),
+:global(.waveform-annotation-editor-root input),
+:global(.waveform-annotation-editor-root select),
+:global(.waveform-annotation-editor-root textarea) {
+  font-family: inherit;
+  letter-spacing: normal;
+  text-transform: none;
+}
+
+:global(.waveform-annotation-editor-root button) {
+  appearance: auto;
+}
+
 .waveform-annotation-editor__content {
   display: grid;
   gap: 20px;

src/components/annotation/WaveformAnnotationEditor.vue

@@ -126,6 +126,7 @@ function handleSeriesChange(event: Event) {
     cancel-text="取消"
     ok-text="保存标注"
     :ok-button-props="{ disabled: !canConfirm }"
+    root-class-name="waveform-annotation-editor-root"
     wrap-class-name="waveform-annotation-editor"
     @cancel="emit('cancel')"
     @ok="confirm"

src/components/annotation/components.test.ts

@@ -18,13 +18,14 @@ const modalStub = defineComponent({
     'cancelText',
     'okText',
     'okButtonProps',
+    'rootClassName',
   ],
   emits: ['cancel', 'ok'],
   setup(props, { emit, slots }) {
     return () => {
       const title = slots.title?.() ?? []
       const titleId = (title[0]?.props as { id?: string } | undefined)?.id
-      return h('div', { class: 'ant-modal-root' }, [
+      return h('div', { class: ['ant-modal-root', props.rootClassName] }, [
         h(
           'div',
           {
@@ -96,6 +97,18 @@ describe('waveform annotation controls', () => {
     expect(second.get('[role="dialog"]').attributes('aria-labelledby')).toBe(secondTitleId)
   })
 
+  it('uses a dedicated root class to isolate teleported modal styles', () => {
+    const wrapper = mountEditor({
+      props: {
+        annotation: { id: 'isolated', seriesId: 'a', x: 1, y: 2, text: '说明' },
+        mode: 'add',
+      },
+    })
+
+    expect(wrapper.get('.ant-modal-root').classes()).toContain('waveform-annotation-editor-root')
+    expect(wrapper.get('.ant-modal-wrap').classes()).toContain('waveform-annotation-editor')
+  })
+
   it.each(['add', 'edit'] as const)('shows the X-axis snapping hint in %s mode', (mode) => {
     const wrapper = mountEditor({
       props: {

src/components/core/fixedYDomainLayout.test.ts

@@ -35,7 +35,7 @@ function track(seriesList: DisplaySeries[]): DisplayTrack {
 }
 
 describe('fixed Y-domain layout', () => {
-  it('uses an exact global fixed domain without applying nice bounds', () => {
+  it('expands a global fixed domain to nice equal intervals', () => {
     const sourceTrack = track([series('a', 0, 100)])
     const result = buildTrackLayouts({
       cells: [
@@ -53,7 +53,13 @@ describe('fixed Y-domain layout', () => {
           series: sourceTrack,
         },
       ],
-      grid: { rowCount: 1, columnCount: 1, showPagination: false, trackLines: {} },
+      grid: {
+        rowCount: 1,
+        columnCount: 1,
+        showPagination: false,
+        fillIncompleteLastRow: false,
+        trackLines: {},
+      },
       displayMode: 'independent',
       overlayMode: 'single-axis',
       independentTransforms: [zoomIdentity],
@@ -66,10 +72,92 @@ describe('fixed Y-domain layout', () => {
       showCompactEmptyTracks: false,
     })[0]
 
-    expect(result?.yScale.domain()).toEqual([3, 97])
+    expect(result?.yScale.domain()).toEqual([0, 100])
-    expect(result?.yAxes[0]?.tickValues).toContain(3)
+    expect(result?.yAxes[0]?.tickValues).toContain(0)
-    expect(result?.yAxes[0]?.tickValues).toContain(97)
+    expect(result?.yAxes[0]?.tickValues).toContain(100)
-    expect(result?.seriesPaths[0]?.yScale.domain()).toEqual([3, 97])
+    expect(result?.seriesPaths[0]?.yScale.domain()).toEqual([0, 100])
+  })
+
+  it('uses the configured split number for fixed domains', () => {
+    const result = buildTrackLayouts({
+      cells: [
+        {
+          slotIndex: 0,
+          row: 0,
+          column: 0,
+          left: 0,
+          top: 0,
+          width: 120,
+          height: 100,
+          plotHeight: 100,
+          cellHeight: 130,
+          xAxisBand: 30,
+          series: track([series('a', 0, 100)]),
+        },
+      ],
+      grid: {
+        rowCount: 1,
+        columnCount: 1,
+        showPagination: false,
+        fillIncompleteLastRow: false,
+        trackLines: {},
+      },
+      displayMode: 'independent',
+      overlayMode: 'single-axis',
+      independentTransforms: [zoomIdentity],
+      sharedZoomDomain: [0, 1],
+      fixedYDomain: [3, 97],
+      yAxisSplitNumber: 5,
+      timeUnit: 'ms',
+      rendering: DEFAULT_WAVEFORM_RENDERING_OPTIONS,
+      hideSecondaryLabels: false,
+      yAxisLabelX: -50,
+      showCompactEmptyTracks: false,
+    })[0]
+
+    expect(result?.yAxes[0]?.majorTicks).toEqual([0, 25, 50, 75, 100])
+  })
+
+  it('defaults to five ticks and supports a two-tick axis', () => {
+    const build = (splitNumber?: number) =>
+      buildTrackLayouts({
+        cells: [
+          {
+            slotIndex: 0,
+            row: 0,
+            column: 0,
+            left: 0,
+            top: 0,
+            width: 120,
+            height: 100,
+            plotHeight: 100,
+            cellHeight: 130,
+            xAxisBand: 30,
+            series: track([series('a', 3, 97)]),
+          },
+        ],
+        grid: {
+          rowCount: 1,
+          columnCount: 1,
+          showPagination: false,
+          fillIncompleteLastRow: false,
+          trackLines: {},
+        },
+        displayMode: 'independent',
+        overlayMode: 'single-axis',
+        independentTransforms: [zoomIdentity],
+        sharedZoomDomain: [0, 1],
+        fixedYDomain: [3, 97],
+        yAxisSplitNumber: splitNumber,
+        timeUnit: 'ms',
+        rendering: DEFAULT_WAVEFORM_RENDERING_OPTIONS,
+        hideSecondaryLabels: false,
+        yAxisLabelX: -50,
+        showCompactEmptyTracks: false,
+      })[0]?.yAxes[0]?.majorTicks
+
+    expect(build()).toHaveLength(5)
+    expect(build(2)).toEqual([0, 100])
   })
 
   it('resolves track, series, and global fixed-domain precedence', () => {

src/components/core/grid.test.ts

@@ -15,12 +15,14 @@ describe('waveform grid helpers', () => {
       rowCount: 2,
       columnCount: 1,
       showPagination: true,
+      fillIncompleteLastRow: false,
       trackLines: {},
     })
     expect(normalizeGridOptions({ rowCount: 0, columnCount: 99 })).toEqual({
       rowCount: 1,
       columnCount: 10,
       showPagination: true,
+      fillIncompleteLastRow: false,
       trackLines: {},
     })
   })
@@ -131,4 +133,50 @@ describe('waveform grid helpers', () => {
     expect(cells[1].left).toBe(232)
     expect(cells[2].top).toBe(cells[0].plotHeight + X_AXIS_BAND + 14)
   })
+
+  it('fills incomplete final rows without changing page capacity', () => {
+    const oneColumn = resolveGridCellGeometry(
+      400,
+      400,
+      normalizeGridOptions({ rowCount: 4, columnCount: 1, fillIncompleteLastRow: true }),
+      'separated',
+      [true, true, true],
+    )
+    expect(oneColumn).toHaveLength(3)
+    expect(oneColumn.map((cell) => cell.width)).toEqual([400, 400, 400])
+    expect(oneColumn.at(-1)?.isLastRow).toBe(true)
+
+    const twoColumns = resolveGridCellGeometry(
+      400,
+      300,
+      normalizeGridOptions({ rowCount: 2, columnCount: 2, fillIncompleteLastRow: true }),
+      'separated',
+      [true, true, true],
+    )
+    expect(twoColumns).toHaveLength(3)
+    expect(twoColumns[2]).toMatchObject({ row: 1, column: 0, left: 0, width: 400 })
+
+    const threeColumns = resolveGridCellGeometry(
+      400,
+      300,
+      normalizeGridOptions({ rowCount: 2, columnCount: 3, fillIncompleteLastRow: true }),
+      'separated',
+      [true, true, true, true, true],
+    )
+    expect(threeColumns).toHaveLength(5)
+    expect(threeColumns.slice(3).map((cell) => cell.width)).toEqual([192, 192])
+    expect(threeColumns.slice(3).map((cell) => cell.left)).toEqual([0, 208])
+  })
+
+  it('keeps full pages and the disabled option byte-for-byte compatible', () => {
+    const base = normalizeGridOptions({ rowCount: 2, columnCount: 2 })
+    const filled = normalizeGridOptions({ rowCount: 2, columnCount: 2, fillIncompleteLastRow: true })
+    const fullSlots = [true, true, true, true]
+    expect(resolveGridCellGeometry(400, 300, filled, 'independent', fullSlots)).toEqual(
+      resolveGridCellGeometry(400, 300, base, 'independent', fullSlots),
+    )
+    expect(resolveGridCellGeometry(400, 300, base, 'independent', [true, true, true])).toHaveLength(
+      4,
+    )
+  })
 })

src/components/core/grid.ts

@@ -8,6 +8,7 @@ export interface WaveformGridOptions {
   rowCount?: number
   columnCount?: number
   showPagination?: boolean
+  fillIncompleteLastRow?: boolean
   trackLines?: WaveformGridTrackLines
 }
 
@@ -33,6 +34,7 @@ export interface NormalizedWaveformGridOptions {
   rowCount: number
   columnCount: number
   showPagination: boolean
+  fillIncompleteLastRow: boolean
   trackLines: Record<string, NormalizedWaveformGridLineOptions>
 }
 
@@ -48,6 +50,7 @@ export interface GridCellGeometry {
   plotHeight: number
   cellHeight: number
   xAxisBand: number
+  isLastRow?: boolean
 }
 
 const normalizeCount = (value: unknown, fallback: number) => {
@@ -78,6 +81,7 @@ export function normalizeGridOptions(options?: WaveformGridOptions): NormalizedW
     rowCount: normalizeCount(options?.rowCount, 2),
     columnCount: normalizeCount(options?.columnCount, 1),
     showPagination: options?.showPagination ?? true,
+    fillIncompleteLastRow: options?.fillIncompleteLastRow ?? false,
     trackLines,
   }
 }
@@ -114,20 +118,23 @@ export function resolveGridCellGeometry(
   horizontalGap?: number,
   showXAxis = true,
 ): GridCellGeometry[] {
+  const pageSize = getPageSize(options)
+  const seriesCount = slotHasSeries.filter(Boolean).length
+  const filledLastRow = options.fillIncompleteLastRow && seriesCount > 0 && seriesCount < pageSize
+  const rowCount = filledLastRow ? Math.ceil(seriesCount / options.columnCount) : options.rowCount
   const defaultGap = getGridGap(displayMode)
   const columnGap = Number.isFinite(horizontalGap)
     ? Math.max(0, horizontalGap as number)
     : defaultGap
-  const totalHorizontalGap = Math.max(0, options.columnCount - 1) * columnGap
   const axisRows = new Set<number>()
   if (!showXAxis) {
     // Net view uses the full drawing area for waveform pixels.
   } else if (displayMode === 'independent') {
-    for (let row = 0; row < options.rowCount; row += 1) axisRows.add(row)
+    for (let row = 0; row < rowCount; row += 1) axisRows.add(row)
   } else if (displayMode === 'compact') {
     // Compact tracks share one continuous plot stack. Reserve the X-axis band
     // only beneath the final grid row, including when that row is empty.
-    axisRows.add(options.rowCount - 1)
+    axisRows.add(rowCount - 1)
   } else {
     for (let column = 0; column < options.columnCount; column += 1) {
       for (let slotIndex = getPageSize(options) - 1; slotIndex >= 0; slotIndex -= 1) {
@@ -139,17 +146,22 @@ export function resolveGridCellGeometry(
       }
     }
   }
-  const totalVerticalGap = Math.max(0, options.rowCount - 1) * defaultGap
+  const totalVerticalGap = Math.max(0, rowCount - 1) * defaultGap
   const totalAxisBand = axisRows.size * X_AXIS_BAND
-  const width = Math.max(1, (innerWidth - totalHorizontalGap) / options.columnCount)
   const plotHeight = Math.max(
     1,
-    (innerHeight - totalVerticalGap - totalAxisBand) / options.rowCount,
+    (innerHeight - totalVerticalGap - totalAxisBand) / rowCount,
   )
 
-  return Array.from({ length: getPageSize(options) }, (_, slotIndex) => {
+  return Array.from({ length: filledLastRow ? seriesCount : pageSize }, (_, slotIndex) => {
     const row = Math.floor(slotIndex / options.columnCount)
     const column = slotIndex % options.columnCount
+    const rowSeriesCount =
+      filledLastRow && row === rowCount - 1
+        ? seriesCount - row * options.columnCount
+        : options.columnCount
+    const rowGap = Math.max(0, rowSeriesCount - 1) * columnGap
+    const width = Math.max(1, (innerWidth - rowGap) / rowSeriesCount)
     const xAxisBand = axisRows.has(row) ? X_AXIS_BAND : 0
     const cellHeight = plotHeight + xAxisBand
     const top = Array.from({ length: row }, (_, previousRow) => {
@@ -167,6 +179,7 @@ export function resolveGridCellGeometry(
       plotHeight,
       cellHeight,
       xAxisBand,
+      isLastRow: row === rowCount - 1,
     }
   })
 }

src/components/core/layout.test.ts

@@ -9,6 +9,7 @@ import {
   findClosestTrackAtPointer,
   MAX_MULTI_Y_AXIS_COUNT,
   measureYAxisGroupClearance,
+  resolveYAxisTickCount,
 } from './layout'
 
 function series(id: string, minimum: number, maximum: number): DisplaySeries {
@@ -64,7 +65,13 @@ function layoutForSeries(
         series: sourceTrack,
       },
     ],
-    grid: { rowCount: 1, columnCount: 1, showPagination: false, trackLines: {} },
+    grid: {
+      rowCount: 1,
+      columnCount: 1,
+      showPagination: false,
+      fillIncompleteLastRow: false,
+      trackLines: {},
+    },
     displayMode: 'independent',
     overlayMode: 'single-axis',
     independentTransforms: [transform],
@@ -106,7 +113,13 @@ describe('multi-value Y-axis grouping', () => {
           series: sourceTrack,
         },
       ],
-      grid: { rowCount: 1, columnCount: 1, showPagination: false, trackLines: {} },
+      grid: {
+        rowCount: 1,
+        columnCount: 1,
+        showPagination: false,
+        fillIncompleteLastRow: false,
+        trackLines: {},
+      },
       displayMode: 'independent',
       overlayMode: 'single-axis',
       independentTransforms: [zoomIdentity],
@@ -119,8 +132,15 @@ describe('multi-value Y-axis grouping', () => {
       showCompactEmptyTracks: false,
     })[0]
 
-    expect(result?.yScale.domain()).toEqual([25, 75])
+    expect(result?.yScale.domain()).toEqual([20, 80])
-    expect(result?.seriesPaths[0]?.yScale.domain()).toEqual([25, 75])
+    expect(result?.seriesPaths[0]?.yScale.domain()).toEqual([20, 80])
+  })
+
+  it('normalizes configured Y-axis split counts', () => {
+    expect(resolveYAxisTickCount(100, 0)).toBe(2)
+    expect(resolveYAxisTickCount(100, 4.8)).toBe(4)
+    expect(resolveYAxisTickCount(100, Number.NaN)).toBe(5)
+    expect(resolveYAxisTickCount(220)).toBe(5)
   })
 
   it('keeps every overlaid series on one axis in single-axis mode', () => {
@@ -209,7 +229,13 @@ describe('multi-value Y-axis grouping', () => {
           series: track([series('left', 1000, 3000), series('right', 1000, 3000)]),
         },
       ],
-      grid: { rowCount: 1, columnCount: 1, showPagination: false, trackLines: {} },
+      grid: {
+        rowCount: 1,
+        columnCount: 1,
+        showPagination: false,
+        fillIncompleteLastRow: false,
+        trackLines: {},
+      },
       displayMode: 'independent',
       overlayMode: 'multi-axis',
       independentTransforms: [zoomIdentity],

src/components/core/layout.ts

@@ -20,6 +20,13 @@ const Y_AXIS_OUTER_PADDING = 4
 const Y_AXIS_LABEL_GAP = 6
 const Y_AXIS_LABEL_BAND_WIDTH = 24
 
+export function resolveYAxisTickCount(_plotHeight: number, splitNumber?: number): number {
+  if (typeof splitNumber === 'number' && Number.isFinite(splitNumber)) {
+    return Math.max(2, Math.floor(splitNumber))
+  }
+  return 5
+}
+
 export interface YAxisSeriesGroup {
   index: number
   side: 'left' | 'right'
@@ -103,16 +110,22 @@ export function axisTextMetrics(
   domain: [number, number],
   nice = true,
   tickValues?: number[],
+  unit?: string,
+  tickCount = 10,
 ): { tickTextWidth: number } {
+  const effectiveTickCount =
+    typeof tickCount === 'number' && Number.isFinite(tickCount)
+      ? Math.max(2, Math.floor(tickCount))
+      : 10
   const scale = scaleLinear(domain, [1, 0])
-  if (nice) scale.nice()
+  if (nice) scale.nice(effectiveTickCount)
   const [axisMin, axisMax] = scale.domain()
-  const values = tickValues ?? Array.from(new Set([axisMin, ...scale.ticks(10), axisMax]))
+  const values = tickValues ?? scale.ticks(effectiveTickCount)
   const topTickValue = Math.max(...values)
   const maximumTickCharacters = Math.max(
     1,
     ...values.map(
-      (value) => formatScientificAxisLabel(value, { axisMin, axisMax, topTickValue }).length,
+      (value) => formatScientificAxisLabel(value, { axisMin, axisMax, topTickValue, unit }).length,
     ),
   )
   return {
@@ -120,9 +133,10 @@ export function axisTextMetrics(
   }
 }
 
-export function measureYAxisGroupClearance(group: YAxisSeriesGroup): number {
+export function measureYAxisGroupClearance(group: YAxisSeriesGroup, tickCount?: number): number {
   return (
-    axisTextMetrics(group.domain, !group.fixed).tickTextWidth +
+    axisTextMetrics(group.domain, true, undefined, group.seriesList[0]?.unit, tickCount)
+      .tickTextWidth +
     Y_AXIS_TICK_PADDING +
     Y_AXIS_LABEL_GAP +
     Y_AXIS_LABEL_BAND_WIDTH +
@@ -130,9 +144,10 @@ export function measureYAxisGroupClearance(group: YAxisSeriesGroup): number {
   )
 }
 
-function measureYAxisGroupTickClearance(group: YAxisSeriesGroup): number {
+function measureYAxisGroupTickClearance(group: YAxisSeriesGroup, tickCount?: number): number {
   return (
-    axisTextMetrics(group.domain, !group.fixed).tickTextWidth +
+    axisTextMetrics(group.domain, true, undefined, group.seriesList[0]?.unit, tickCount)
+      .tickTextWidth +
     Y_AXIS_TICK_PADDING +
     Y_AXIS_OUTER_PADDING
   )
@@ -143,13 +158,14 @@ export function measureTrackYAxisClearance(
   overlayMode: WaveformOverlayMode,
   yDomain?: WaveformYDomain,
   yDomains?: Record<string, WaveformYDomain>,
+  tickCount?: number,
 ): { left: number; right: number } {
   return resolveYAxisSeriesGroups(track, overlayMode, yDomain, yDomains).reduce(
     (clearance, group) => {
       clearance[group.side] +=
         overlayMode === 'multi-axis' || track.visibleSeries.length === 1
-          ? measureYAxisGroupClearance(group)
+          ? measureYAxisGroupClearance(group, tickCount)
-          : measureYAxisGroupTickClearance(group)
+          : measureYAxisGroupTickClearance(group, tickCount)
       return clearance
     },
     { left: 0, right: 0 },

src/components/core/trackLayoutBuilder.ts

@@ -25,7 +25,7 @@ import {
   type GridCellGeometry,
   type NormalizedWaveformGridOptions,
 } from './grid'
-import { axisTextMetrics, resolveYAxisSeriesGroups } from './layout'
+import { axisTextMetrics, resolveYAxisSeriesGroups, resolveYAxisTickCount } from './layout'
 import type { DisplaySeries, DisplayTrack, TrackLayout, WaveformYAxisLayout } from './types'
 import { applyXDomainStrategy } from './xDomain'
 import {
@@ -54,6 +54,7 @@ export interface BuildTrackLayoutsOptions {
   yDomains?: Record<string, [number, number]>
   timeUnit: 's' | 'ms'
   xAxisLabelFormatter?: WaveformXAxisLabelFormatter
+  yAxisSplitNumber?: number
   rendering: ResolvedWaveformRenderingOptions
   hideSecondaryLabels: boolean
   yAxisLabelX: number
@@ -124,18 +125,27 @@ export function buildTrackLayouts(options: BuildTrackLayoutsOptions): TrackLayou
     )
     const sideOffsets = { left: 0, right: 0 }
     const yAxes: WaveformYAxisLayout[] = yAxisGroups.map((group) => {
+      const tickCount = resolveYAxisTickCount(cell.plotHeight, options.yAxisSplitNumber)
+      const niceCount = Math.max(1, tickCount - 1)
       const scale = scaleLinear(group.domain, [cell.plotHeight, 0])
-      if (!group.fixed) scale.nice()
+      scale.nice(niceCount)
-      const majorTicks = scale.ticks(Math.max(2, Math.floor(cell.plotHeight / 55)))
       const [axisStart, axisEnd] = scale.domain()
+      const majorTicks = Array.from(
+        { length: tickCount },
+        (_, index) => axisStart + ((axisEnd - axisStart) * index) / (tickCount - 1),
+      )
       const showAxisEnd = options.displayMode !== 'compact' || cell.row === 0
       const visibleMajorTicks = showAxisEnd
         ? majorTicks
         : majorTicks.filter((tick) => tick !== axisEnd)
-      const tickValues = Array.from(
+      const tickValues = visibleMajorTicks
-        new Set([axisStart, ...visibleMajorTicks, ...(showAxisEnd ? [axisEnd] : [])]),
+      const { tickTextWidth } = axisTextMetrics(
+        scale.domain() as [number, number],
+        false,
+        tickValues,
+        group.seriesList[0]?.unit,
+        tickCount,
       )
-      const { tickTextWidth } = axisTextMetrics(group.domain, !group.fixed, tickValues)
       const clearance =
         tickTextWidth +
         Y_AXIS_TICK_PADDING +
@@ -256,7 +266,7 @@ export function buildTrackLayouts(options: BuildTrackLayoutsOptions): TrackLayou
         (isEmpty || hasVisibleSeries) &&
         (options.displayMode === 'independent' ||
           (options.displayMode === 'compact'
-            ? cell.row === options.grid.rowCount - 1
+            ? (cell.isLastRow ?? cell.row === options.grid.rowCount - 1)
             : bottomCells.has(cell.slotIndex))),
     }
   })

src/components/core/useWaveformChartController.ts

@@ -259,6 +259,9 @@ export function useWaveformChartController(
     trackLayouts,
     innerWidth,
     innerHeight,
+    sharedZoomDomain,
+    initialXDomain,
+    sharedTransform,
     activeInteractionMode,
     hiddenSeriesIdSet,
     internalHiddenSeriesIds,

src/components/core/useWaveformChartLifecycle.ts

@@ -11,6 +11,7 @@ import {
 
 import type { AnnotationSeriesCandidate } from '../annotation'
 import type { useWaveformAnnotationInteraction } from '../annotation'
+import type { NormalizedWaveformGridOptions } from './grid'
 import type { DisplaySeries, DisplayTrack, TrackLayout } from './types'
 import type { ResolvedWaveformChartProps, WaveformChartEmit } from './waveformChartTypes'
 import { constrainZoomDomain, transformForDomain } from '../interaction/zoomConstraints'
@@ -33,12 +34,15 @@ interface LifecycleContext {
   currentPage: Ref<number>
   pageCount: ComputedRef<number>
   pagedTracks: ComputedRef<Array<DisplayTrack | undefined>>
-  gridOptions: ComputedRef<{ rowCount: number; columnCount: number }>
+  gridOptions: ComputedRef<NormalizedWaveformGridOptions>
   chartSeries: ComputedRef<DisplaySeries[]>
   chartTracks: ComputedRef<DisplayTrack[]>
   trackLayouts: ComputedRef<TrackLayout[]>
   innerWidth: ComputedRef<number>
   innerHeight: ComputedRef<number>
+  sharedZoomDomain: ComputedRef<[number, number]>
+  initialXDomain: ComputedRef<[number, number]>
+  sharedTransform: ShallowRef<ZoomTransform>
   activeInteractionMode: ComputedRef<string | undefined>
   hiddenSeriesIdSet: ComputedRef<Set<string>>
   internalHiddenSeriesIds: Ref<Set<string>>
@@ -93,6 +97,9 @@ export function useWaveformChartLifecycle(context: LifecycleContext) {
     trackLayouts,
     innerWidth,
     innerHeight,
+    sharedZoomDomain,
+    initialXDomain,
+    sharedTransform,
     activeInteractionMode,
     hiddenSeriesIdSet,
     internalHiddenSeriesIds,
@@ -144,25 +151,24 @@ export function useWaveformChartLifecycle(context: LifecycleContext) {
     emit('page-change', nextPage, pageCount.value)
   }
 
+  let pendingSharedXDomain: [number, number] | undefined
   let pendingIndependentXDomains: Array<[number, number] | undefined> | undefined
 
   function handleBeforeDataReferenceChange() {
-    if (props.displayMode !== 'independent') return
+    if (props.displayMode === 'independent') {
+      pendingSharedXDomain = undefined
       pendingIndependentXDomains = trackLayouts.value.map((track) => {
-      const configuredDomain =
+        const current = track.xScale.domain() as [number, number]
-        props.initialXDomains?.[track.series.trackId ?? track.series.id] ??
+        const boundary = resolveInitialTrackDomain(track)
-        props.initialXDomains?.[track.series.id] ??
+        return current[1] - current[0] < boundary[1] - boundary[0] - 1e-12 ? current : undefined
-        props.initialXDomain
-      if (
-        !configuredDomain ||
-        !Number.isFinite(configuredDomain[0]) ||
-        !Number.isFinite(configuredDomain[1]) ||
-        configuredDomain[0] === configuredDomain[1]
-      ) {
-        return undefined
-      }
-      return track.xScale.domain() as [number, number]
       })
+      return
+    }
+    pendingIndependentXDomains = undefined
+    const current = sharedZoomDomain.value
+    const boundary = initialXDomain.value
+    pendingSharedXDomain =
+      current[1] - current[0] < boundary[1] - boundary[0] - 1e-12 ? [...current] : undefined
   }
 
   function handleDataReferenceChange() {
@@ -186,10 +192,15 @@ export function useWaveformChartLifecycle(context: LifecycleContext) {
         })
         independentTransforms.value = nextTransforms
         pendingIndependentXDomains = undefined
-        void nextTick(configureZoom)
+      } else if (props.displayMode !== 'independent' && pendingSharedXDomain) {
-        return
+        const boundary = initialXDomain.value
+        const groups = trackLayouts.value
+          .filter((track) => track.hasVisibleSeries)
+          .map((track) => track.seriesList)
+        const domain = constrainZoomDomain(pendingSharedXDomain, boundary, groups, props)
+        sharedTransform.value = transformForDomain(domain, boundary, innerWidth.value)
+        pendingSharedXDomain = undefined
       }
-      pendingIndependentXDomains = undefined
       configureZoom()
     })
   }
@@ -210,6 +221,7 @@ export function useWaveformChartLifecycle(context: LifecycleContext) {
       currentPage,
       () => gridOptions.value.rowCount,
       () => gridOptions.value.columnCount,
+      () => gridOptions.value.fillIncompleteLastRow,
       activeInteractionMode,
     ],
     async () => {
@@ -229,7 +241,14 @@ export function useWaveformChartLifecycle(context: LifecycleContext) {
     },
   )
 
-  watch([pageCount, () => props.grid?.rowCount, () => props.grid?.columnCount], () => {
+  watch(
+    [
+      pageCount,
+      () => props.grid?.rowCount,
+      () => props.grid?.columnCount,
+      () => props.grid?.fillIncompleteLastRow,
+    ],
+    () => {
       const previousPage = currentPage.value
       currentPage.value =
         currentPage.value > pageCount.value
@@ -242,7 +261,8 @@ export function useWaveformChartLifecycle(context: LifecycleContext) {
       }
       clearHover()
       void nextTick(configureZoom)
-  })
+    },
+  )
 
   watch(activeInteractionMode, () => {
     editorSeriesOptions.value = []

src/components/core/useWaveformLayout.ts

@@ -112,7 +112,16 @@ export function useWaveformLayout(context: LayoutContext) {
       .flatMap((track) =>
         resolveYAxisSeriesGroups(track, props.overlayMode, props.yDomain, props.yDomains),
       )
-      .map((group) => axisTextMetrics(group.domain, !group.fixed).tickTextWidth)
+      .map(
+        (group) =>
+          axisTextMetrics(
+            group.domain,
+            true,
+            undefined,
+            group.seriesList[0]?.unit,
+            props.axes?.y?.splitNumber,
+          ).tickTextWidth,
+      )
     const tickTextWidth = Math.max(Y_AXIS_CHARACTER_WIDTH, ...axisText)
     const tickClearance = tickTextWidth + Y_AXIS_TICK_PADDING + Y_AXIS_OUTER_PADDING
     const labelCenterX = -(
@@ -157,6 +166,7 @@ export function useWaveformLayout(context: LayoutContext) {
           props.overlayMode,
           props.yDomain,
           props.yDomains,
+          props.axes?.y?.splitNumber,
         )
         return {
           left: Math.max(maximum.left, clearance.left),
@@ -298,6 +308,7 @@ export function useWaveformLayout(context: LayoutContext) {
           : sharedYDomains.value,
       timeUnit: props.timeUnit,
       xAxisLabelFormatter: props.axes?.x?.labelFormatter,
+      yAxisSplitNumber: props.axes?.y?.splitNumber,
       rendering: renderingOptions.value,
       hideSecondaryLabels: isCleanView.value || yAxisLayout.value.hideSecondaryLabels,
       yAxisLabelX: yAxisMetrics.value.labelCenterX,

src/components/interaction/useWaveformViewport.ts

@@ -11,6 +11,7 @@ import type {
 import type { AnnotationSeriesCandidate } from '../annotation'
 import { tryReleasePointerCapture } from './pointerCapture'
 import { transitionViewportInteraction } from './viewportInteractionState'
+import { createViewportDomainSetter } from './viewportDomain'
 import { constrainZoomDomain, transformForDomain } from './zoomConstraints'
 interface ViewportContext {
   props: ResolvedWaveformChartProps
@@ -344,6 +345,20 @@ export function useWaveformViewport(context: ViewportContext) {
     editorSeriesOptions.value = []
     void nextTick(configureZoom)
   }
+  const setViewportDomain = createViewportDomainSetter({
+    props,
+    trackLayouts,
+    initialXDomain,
+    resolveInitialTrackDomain,
+    innerWidth,
+    sharedTransform,
+    independentTransforms,
+    cancelPendingZoom,
+    cancelViewportDrag,
+    clearHover,
+    editorSeriesOptions,
+    configureZoom,
+  })
   const requestViewportReset = (event: MouseEvent) => {
     if (isPresentationMode.value || !props.zoomable || !isZoomMode.value) return
     if (props.displayMode === 'independent') {
@@ -372,6 +387,7 @@ export function useWaveformViewport(context: ViewportContext) {
     finishViewportDrag,
     cancelViewportDrag,
     resetViewport,
+    setViewportDomain,
     requestViewportReset,
   }
 }

src/components/interaction/viewportDomain.ts

@@ -0,0 +1,60 @@
+import { nextTick, type ComputedRef, type Ref, type ShallowRef } from 'vue'
+import type { ZoomTransform } from 'd3'
+
+import type { TrackLayout } from '../core/types'
+import type { ResolvedWaveformChartProps } from '../core/waveformChartTypes'
+import type { AnnotationSeriesCandidate } from '../annotation'
+import { constrainZoomDomain, transformForDomain } from './zoomConstraints'
+
+interface ViewportDomainContext {
+  props: ResolvedWaveformChartProps
+  trackLayouts: ComputedRef<TrackLayout[]>
+  initialXDomain: ComputedRef<[number, number]>
+  resolveInitialTrackDomain: (track: TrackLayout) => [number, number]
+  innerWidth: ComputedRef<number>
+  sharedTransform: ShallowRef<ZoomTransform>
+  independentTransforms: ShallowRef<ZoomTransform[]>
+  cancelPendingZoom: () => void
+  cancelViewportDrag: () => void
+  clearHover: () => void
+  editorSeriesOptions: Ref<AnnotationSeriesCandidate[]>
+  configureZoom: () => void
+}
+
+export function createViewportDomainSetter(context: ViewportDomainContext) {
+  return (domain: [number, number], trackIndex?: number) => {
+    if (!Number.isFinite(domain[0]) || !Number.isFinite(domain[1]) || domain[0] === domain[1])
+      return
+    context.cancelPendingZoom()
+    context.cancelViewportDrag()
+    if (context.props.displayMode === 'independent') {
+      const indexes =
+        trackIndex === undefined
+          ? context.trackLayouts.value.map((track) => track.index)
+          : [trackIndex]
+      const nextTransforms = [...context.independentTransforms.value]
+      indexes.forEach((index) => {
+        const track = context.trackLayouts.value.find((item) => item.index === index)
+        if (!track) return
+        const boundary = context.resolveInitialTrackDomain(track)
+        const constrained = constrainZoomDomain(domain, boundary, [track.seriesList], context.props)
+        nextTransforms[index] = transformForDomain(constrained, boundary, track.width)
+      })
+      context.independentTransforms.value = nextTransforms
+    } else {
+      const boundary = context.initialXDomain.value
+      const groups = context.trackLayouts.value
+        .filter((track) => track.hasVisibleSeries)
+        .map((track) => track.seriesList)
+      const constrained = constrainZoomDomain(domain, boundary, groups, context.props)
+      context.sharedTransform.value = transformForDomain(
+        constrained,
+        boundary,
+        context.innerWidth.value,
+      )
+    }
+    context.clearHover()
+    context.editorSeriesOptions.value = []
+    void nextTick(context.configureZoom)
+  }
+}

src/components/rendering/WaveformTrackAxes.vue

@@ -44,9 +44,10 @@ function renderAxes() {
     if (!element) return
     const [axisMin, axisMax] = axis.scale.domain()
     const topTickValue = Math.max(...axis.tickValues)
+    const unit = axis.seriesList[0]?.unit
     const yAxis = (axis.side === 'left' ? axisLeft(axis.scale) : axisRight(axis.scale))
       .tickFormat((value) =>
-        formatScientificAxisLabel(Number(value), { axisMin, axisMax, topTickValue }),
+        formatScientificAxisLabel(Number(value), { axisMin, axisMax, topTickValue, unit }),
       )
       .tickSize(-4)
       .tickPadding(7)

src/components/waveformChartCases/compactAndSharedHover.test.ts

@@ -65,9 +65,9 @@ describe('WaveformChart', () => {
     )
 
     expect(endTicks[0]).toHaveLength(1)
-    expect(Number(endTicks[0][0].text())).toBe(0.9)
+    expect(Number(endTicks[0][0].text())).toBe(1)
     expect(endTicks[1]).toHaveLength(1)
-    expect(Number(endTicks[1][0].text())).toBe(1.9)
+    expect(Number(endTicks[1][0].text())).toBe(2)
     expect(endTicks[2]).toHaveLength(0)
     expect(endTicks[3]).toHaveLength(0)
   })

src/components/waveformChartCases/dataLifecycle.test.ts

@@ -158,6 +158,12 @@ describe('WaveformChart', () => {
     expect(paths[0].attributes('data-series-name')).toBe('BT2_2M')
     const yAxisLabels = wrapper.findAll('.waveform-chart__y-axis-label')
     expect(yAxisLabels.map((label) => label.text())).toEqual(['BT2_2M', 'BT1_2M'])
+    expect(
+      wrapper
+        .findAll('.waveform-chart__axis--y .tick text')
+        .map((label) => label.text())
+        .some((label) => label.includes('(T)')),
+    ).toBe(true)
     expect(yAxisLabels.map((label) => label.attributes('fill'))).toEqual(['#0960bd', '#ff7f0e'])
     const labelX = Number(
       yAxisLabels[0].attributes('transform')?.match(/^translate\(([-\d.]+),/)?.[1],
@@ -255,7 +261,7 @@ describe('WaveformChart', () => {
       })
 
       expect(startTicks).toHaveLength(1)
-      expect(Number(startTicks[0].text())).toBe(0.1)
+      expect(Number(startTicks[0].text())).toBe(0)
     },
   )
 
@@ -291,7 +297,7 @@ describe('WaveformChart', () => {
         { displayMode },
       )
 
-      const expectedEndValues = [0.9, 4.9]
+      const expectedEndValues = [1, 5]
       wrapper.findAll('.waveform-chart__track').forEach((track, index) => {
         const endTicks = track.findAll('.waveform-chart__axis--y .tick').filter((tick) => {
           const match = tick.attributes('transform')?.match(/translate\(0,\s*([\d.]+)\)/)

src/components/waveformChartCases/gridFill.test.ts

@@ -0,0 +1,95 @@
+import { flushPromises } from '@vue/test-utils'
+import { describe, expect, it } from 'vitest'
+
+import { gridSeries, mountSizedChart } from '../../test/waveformChart'
+
+function geometry(track: { attributes: (name: string) => string | undefined }) {
+  return {
+    left: Number(track.attributes('data-track-left')),
+    top: Number(track.attributes('data-track-top')),
+    width: Number(track.attributes('data-track-width')),
+    height: Number(track.attributes('data-track-height')),
+  }
+}
+
+describe('WaveformChart incomplete grid rows', () => {
+  it.each(['independent', 'separated', 'compact'] as const)(
+    'fills an incomplete two by two row in %s mode',
+    async (displayMode) => {
+      const wrapper = await mountSizedChart(gridSeries(3), {
+        displayMode,
+        grid: { rowCount: 2, columnCount: 2, fillIncompleteLastRow: true },
+      })
+      const tracks = wrapper.findAll('.waveform-chart__track')
+      const first = geometry(tracks[0]!)
+      const last = geometry(tracks[2]!)
+
+      expect(tracks).toHaveLength(3)
+      expect(wrapper.findAll('.waveform-chart__track--empty')).toHaveLength(0)
+      expect(wrapper.findAll('.waveform-chart__grid-slot-placeholder')).toHaveLength(0)
+      expect(last.left).toBe(0)
+      expect(last.width).toBeGreaterThan(first.width * 1.8)
+      expect(last.top).toBeGreaterThan(first.top)
+      if (displayMode === 'independent') {
+        const overlays = wrapper.findAll('.waveform-chart__overlay--independent')
+        expect(overlays).toHaveLength(3)
+        expect(Number(overlays[2]?.attributes('width'))).toBe(last.width)
+      } else {
+        expect(wrapper.findAll('.waveform-chart__overlay--shared')).toHaveLength(1)
+      }
+    },
+  )
+
+  it('removes unused one-column rows and redistributes chart height', async () => {
+    const base = await mountSizedChart(gridSeries(3), {
+      displayMode: 'independent',
+      grid: { rowCount: 4, columnCount: 1 },
+    })
+    const filled = await mountSizedChart(gridSeries(3), {
+      displayMode: 'independent',
+      grid: { rowCount: 4, columnCount: 1, fillIncompleteLastRow: true },
+    })
+    const baseFirst = geometry(base.findAll('.waveform-chart__track')[0]!)
+    const filledTracks = filled.findAll('.waveform-chart__track')
+    const filledFirst = geometry(filledTracks[0]!)
+    const filledLast = geometry(filledTracks[2]!)
+
+    expect(filledTracks).toHaveLength(3)
+    expect(filledFirst.height).toBeGreaterThan(baseFirst.height)
+    expect(filledLast.top + filledLast.height).toBeGreaterThan(baseFirst.height * 3)
+  })
+
+  it('keeps the final two tracks evenly distributed in a two by three grid', async () => {
+    const wrapper = await mountSizedChart(gridSeries(5), {
+      displayMode: 'separated',
+      grid: { rowCount: 2, columnCount: 3, fillIncompleteLastRow: true },
+    })
+    const tracks = wrapper.findAll('.waveform-chart__track').map(geometry)
+
+    expect(tracks).toHaveLength(5)
+    expect(tracks[3]?.left).toBe(0)
+    expect(tracks[3]?.width).toBeCloseTo(tracks[4]?.width ?? 0)
+    expect(tracks[4]?.left).toBeGreaterThan((tracks[3]?.width ?? 0) + 1)
+  })
+
+  it('keeps full pages unchanged and fills a partial second page', async () => {
+    const data = gridSeries(5)
+    const standard = await mountSizedChart(data, {
+      displayMode: 'separated',
+      grid: { rowCount: 2, columnCount: 2 },
+    })
+    const filled = await mountSizedChart(data, {
+      displayMode: 'separated',
+      grid: { rowCount: 2, columnCount: 2, fillIncompleteLastRow: true },
+    })
+    const standardFirstPage = standard.findAll('.waveform-chart__track').map(geometry)
+    expect(filled.findAll('.waveform-chart__track').map(geometry)).toEqual(standardFirstPage)
+
+    await filled.get('.ant-pagination-next button').trigger('click')
+    await flushPromises()
+    const secondPage = filled.findAll('.waveform-chart__track').map(geometry)
+    expect(secondPage).toHaveLength(1)
+    expect(secondPage[0]?.left).toBe(0)
+    expect(secondPage[0]?.width).toBeGreaterThan(standardFirstPage[0]?.width ?? 0)
+  })
+})

src/components/waveformChartCases/layoutAndDomains.test.ts

@@ -6,6 +6,26 @@ import { resizeObservers } from '../../test/setup'
 import { gridSeries, mountSizedChart } from '../../test/waveformChart'
 
 describe('WaveformChart', () => {
+  it('applies the configured Y-axis split number', async () => {
+    const wrapper = await mountSizedChart(
+      {
+        kind: 'points',
+        points: [
+          { x: 0, y: 3 },
+          { x: 1, y: 97 },
+        ],
+      },
+      { axes: { y: { splitNumber: 5 } } },
+    )
+
+    expect(
+      wrapper
+        .get('.waveform-chart__axis--y')
+        .findAll('.tick text')
+        .map((tick) => tick.text()),
+    ).toEqual(['0', '25', '50', '75', '100'])
+  })
+
   it('expands the Y-axis label gutter for signed values and long exponents', async () => {
     const wrapper = await mountSizedChart(
       {
@@ -296,7 +316,7 @@ describe('WaveformChart', () => {
     expect(wrapper.get('.waveform-chart__axis-endpoint--end').text()).toBe('1000')
   })
 
-  it('reacts to exact fixed Y-domain props and returns to automatic bounds', async () => {
+  it('reacts to nice fixed Y-domain props and returns to automatic bounds', async () => {
     const wrapper = await mountSizedChart({
       kind: 'points',
       points: [
@@ -312,8 +332,8 @@ describe('WaveformChart', () => {
 
     await wrapper.setProps({ yDomain: [3, 97] })
     await flushPromises()
-    expect(yTickLabels()).toContain('3')
+    expect(yTickLabels()).toContain('0')
-    expect(yTickLabels()).toContain('97')
+    expect(yTickLabels()).toContain('100')
 
     await wrapper.setProps({ yDomain: undefined })
     await flushPromises()

src/components/waveformChartCases/multiAxisAndPagination.test.ts

@@ -15,6 +15,7 @@ describe('WaveformChart', () => {
           {
             trackId: 'shared-frame',
             name: '普通量程',
+            unit: 'V',
             data: {
               kind: 'points',
               points: [
@@ -26,6 +27,7 @@ describe('WaveformChart', () => {
           {
             trackId: 'shared-frame',
             name: '大量程',
+            unit: 'A',
             data: {
               kind: 'points',
               points: [
@@ -37,6 +39,7 @@ describe('WaveformChart', () => {
           {
             trackId: 'shared-frame',
             name: '小量程',
+            unit: 'T',
             data: {
               kind: 'points',
               points: [
@@ -57,7 +60,11 @@ describe('WaveformChart', () => {
           .map((label) => label.text())
           .filter((label) => label.startsWith('E')),
       ),
-    ).toEqual([[], [expect.stringMatching(/^E\+03 /)], [expect.stringMatching(/^E-04 /)]])
+    ).toEqual([
+      [],
+      [expect.stringMatching(/^E\+03 \(A\) /)],
+      [expect.stringMatching(/^E-04 \(T\) /)],
+    ])
   })
 
   it('reprojects annotations with the Y axis assigned to their series', async () => {

src/components/waveformChartCases/viewportReset.test.ts

@@ -119,6 +119,108 @@ describe('WaveformChart viewport reset', () => {
     expect(wrapper.findAll('.waveform-chart__axis-endpoint--end')[0].text()).toBe('1000')
   })
 
+  it('keeps a controlled shared viewport when the data reference changes', async () => {
+    const wrapper = await mountSizedChart(
+      {
+        kind: 'points',
+        points: [
+          { x: 0, y: 0 },
+          { x: 1, y: 1 },
+        ],
+      },
+      { displayMode: 'separated' },
+    )
+    const chart = wrapper.vm as unknown as {
+      setViewportDomain: (domain: [number, number], trackIndex?: number) => void
+    }
+    chart.setViewportDomain([0.25, 0.75])
+    await flushPromises()
+
+    const startBefore = Number(wrapper.get('.waveform-chart__axis-endpoint--start').text())
+    const endBefore = Number(wrapper.get('.waveform-chart__axis-endpoint--end').text())
+    expect(startBefore).toBeGreaterThan(0)
+    expect(endBefore).toBeLessThan(1000)
+
+    await wrapper.setProps({
+      data: {
+        kind: 'points',
+        points: [
+          { x: 0, y: 10 },
+          { x: 1, y: 11 },
+        ],
+      },
+    })
+    await flushPromises()
+
+    expect(Number(wrapper.get('.waveform-chart__axis-endpoint--start').text())).toBeCloseTo(
+      startBefore,
+      10,
+    )
+    expect(Number(wrapper.get('.waveform-chart__axis-endpoint--end').text())).toBeCloseTo(
+      endBefore,
+      10,
+    )
+  })
+
+  it('keeps independently controlled track viewports when the data reference changes', async () => {
+    const wrapper = await mountSizedChart(gridSeries(2), {
+      displayMode: 'independent',
+      grid: { rowCount: 1, columnCount: 2 },
+    })
+    const chart = wrapper.vm as unknown as {
+      setViewportDomain: (domain: [number, number], trackIndex?: number) => void
+    }
+    chart.setViewportDomain([0.2, 0.8], 0)
+    chart.setViewportDomain([0.1, 0.9], 1)
+    await flushPromises()
+
+    const endpoints = () =>
+      wrapper.findAll('.waveform-chart__track').map((track) => ({
+        start: track.get('.waveform-chart__axis-endpoint--start').text(),
+        end: track.get('.waveform-chart__axis-endpoint--end').text(),
+      }))
+    const endpointsBefore = endpoints()
+    expect(Number(endpointsBefore[0].start)).toBeGreaterThan(0)
+    expect(Number(endpointsBefore[0].end)).toBeLessThan(1000)
+    expect(Number(endpointsBefore[1].start)).toBeGreaterThan(0)
+    expect(Number(endpointsBefore[1].end)).toBeLessThan(1000)
+
+    await wrapper.setProps({ data: gridSeries(2) })
+    await flushPromises()
+
+    const endpointsAfter = endpoints()
+    endpointsAfter.forEach((endpoint, index) => {
+      expect(Number(endpoint.start)).toBeCloseTo(Number(endpointsBefore[index].start), 10)
+      expect(Number(endpoint.end)).toBeCloseTo(Number(endpointsBefore[index].end), 10)
+    })
+  })
+
+  it('ignores invalid domains and applies viewport constraints', async () => {
+    const wrapper = await mountSizedChart(
+      {
+        kind: 'points',
+        points: [
+          { x: 0, y: 0 },
+          { x: 1, y: 1 },
+        ],
+      },
+      { displayMode: 'separated', minZoomSpan: 0.2 },
+    )
+    const chart = wrapper.vm as unknown as {
+      setViewportDomain: (domain: [number, number], trackIndex?: number) => void
+    }
+    chart.setViewportDomain([Number.NaN, 0.5])
+    await flushPromises()
+    expect(wrapper.get('.waveform-chart__axis-endpoint--start').text()).toBe('0')
+    expect(wrapper.get('.waveform-chart__axis-endpoint--end').text()).toBe('1000')
+
+    chart.setViewportDomain([0.49, 0.51])
+    await flushPromises()
+    const start = Number(wrapper.get('.waveform-chart__axis-endpoint--start').text())
+    const end = Number(wrapper.get('.waveform-chart__axis-endpoint--end').text())
+    expect(end - start).toBeGreaterThanOrEqual(200)
+  })
+
   it('resets shared and independent explicit domains to their included nice bounds', async () => {
     const shared = await mountSizedChart(
       {

src/types/chart.ts

@@ -174,6 +174,8 @@ export interface WaveformAxesOptions {
   }
   y?: {
     lineVisible?: boolean
+    /** Target total number of equal Y-axis ticks, including endpoints. Defaults to 5. */
+    splitNumber?: number
   }
 }
 

src/utils/formatters.test.ts

@@ -40,6 +40,15 @@ describe('waveform number formatters', () => {
     expect(formatScientificAxisExponent(0.0001, 0.0003)).toBe('E-04')
   })
 
+  it('appends a unit to the top tick with or without scientific notation', () => {
+    expect(formatScientificAxisLabel(3000, { axisMin: 1000, axisMax: 3000, unit: 'V' })).toBe(
+      'E+03 (V) 3',
+    )
+    expect(formatScientificAxisLabel(3, { axisMin: 0, axisMax: 3, unit: 'A' })).toBe('(A) 3')
+    expect(formatScientificAxisLabel(2, { axisMin: 0, axisMax: 3, unit: 'A' })).toBe('2')
+    expect(formatScientificAxisLabel(3, { axisMin: 0, axisMax: 3, unit: '  ' })).toBe('3')
+  })
+
   it('derives the exponent from the largest absolute endpoint', () => {
     expect(resolveScientificAxisExponent(-9000, -1000)).toBe(3)
     expect(resolveScientificAxisExponent(-100_000, -3000)).toBe(5)

src/utils/formatters.ts

@@ -11,6 +11,7 @@ export interface ScientificAxisLabelOptions {
   axisMin?: number
   axisMax?: number
   topTickValue?: number
+  unit?: string
 }
 
 /** @deprecated Use ScientificAxisLabelOptions. */
@@ -71,9 +72,11 @@ export function formatScientificAxisLabel(
   const scaledValue = exponent === null ? value : value / 10 ** exponent
   const formattedValue = formatYAxisNumber(scaledValue)
   const topTickValue = options.topTickValue ?? options.axisMax
-  return exponent !== null && value === topTickValue
+  if (value !== topTickValue) return formattedValue
-    ? `${formatExponent(exponent)} ${formattedValue}`
+  const unit = options.unit?.trim()
-    : formattedValue
+  const unitLabel = unit ? `(${unit}) ` : ''
+  const exponentLabel = exponent === null ? '' : `${formatExponent(exponent)} `
+  return `${exponentLabel}${unitLabel}${formattedValue}`
 }
 
 /** Return the shared E-style multiplier for an axis, or null for a plain axis. */